Head lamp lens



Aug. 18, 1931. A; Y. DODGE HEAD LAMP LENS Filed Api'il 4, 1928 3Sheets-Sheet l fivenfor':

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Aug. 18, 1931.

A. Y. DODGE 1,819,283

HEAD LAMP LENS 3 Sheets-Sheet 2 Filed April 4, 1928 22 *22 2/ 2o 20 2/ 3/9 A2 /9 fiwenfor: 1719'. 5- %M Jig/62,71, i M

Aug. 18, 1931. A. Y. DODGE 1,319,233

HEAD LAMP LENS Filed April 4, 1928 s Sheets-Sheet s Patented Aug. 18,1931 ADIEL Y. DODGE, OF SOUTH BEND, INDIANA new LAMP LENS Applicationfiled April 4, 1928. Serial No. 267,173.

My invention relates to light controlling apparatus and morespecifically to automobile headlight construction, and is an improvementover the construction described in my co-pending application, Serial No.256,896, filed February 25, 1928.

It is a Well known fact in the art pertaining to head lamps that theposition of the filament with relation to the focal point of theordinary parabolic reflector may vary considerably in any direction dueto permissible tolerances allowable for errors in manufacture, causing aconvergence or divergence of the rays projected from the reflectordepending on the position of the filament.

If the filament is exactly at the-focal point of a parabolic reflector,the reflected rays will be parallel. If in front of the focal point therays will converge; if back of the focal point the rays will diverge; ifabove the focal point the rays in the rear of the focal plane will beprojected downwardly;

and if below the focal point the rays in the rear of the focal planewill be projected upwardly, the degree of these angular projectionsbeing relative to the distance of the filament from the focal point ofthe reflector. It is also possible that the projected rays may convergeor diverge in various angular directions as a resultant of the angulardis placement of the filament from the focal point with relation to thevertical and horizontal axes of the reflector. It is sometimes desirableto use a two filament bulb with the filaments on thevertical axis. Withthis bulb the driver can usewhichever one of the filaments desired, theupper filament being used to project the beam downwardly when anothercar is approaching.

In the head lamps using the ordinary lens, the resulting light patternmay be projected at various angles and distorted to such an extent as tocause glare.

In my invention I have overcome these objections and it has for one ofits objects to provide an improved lens for use with a standardparabolic reflector and a two-filament bulb to produce a high or lowbeam of light, the resultant light patterns remalning substantially thesame in both cases.

Another object is to provide an improved lens for automobile head lampswhich will focus the rays of light to produce a desired pattern undervarious positions of the filament with relation to the focal point ofthe reflector.

Another object is to provide a lens for use with a standard parabolicreflector and a two-filament bulb in which sensitivity to themisplacement of the filament is minimized and which will produce adesirable light pattern in the upper beam, created by the lowerfilament, and substantially the same pattern in the lower beam, createdby the upper filament, but descending at an angle of approximately from2 to 2 degrees low-' er than the upper beams.

Further objects will appear from the description and claims.

In the drawings in which an embodiment of my invention is shown,

Figure 1 is an axial vertical section through a headlight constructionincorporating my invention;

Fig. 2 is a diagrammatic view showing the light pattern as it appears onavertical screen at a distance from the head lamp;

Fig. 3 is a rear elevation of the lens;

Fig. 4 is a section substantially on the line 44 of Fig. 3;

FFig. 5 is a section on the line 55 of Fig. 6 is a diagrammatic Viewillustrating the vertical and'horizontal distribution of light rays; and

Fig. 7 is a diagrammatic view showing the vertical light distribution ofthe lens.

Referring now to the drawings in detail, the construction showncomprises a casing 1 usually of sheet metal and having a parabolicreflector 2 mounted therein. A lens 3 is mounted in front of thereflector and secured by anysuitable retainer such as the erably oneabove and one slightly below the focal point.

The lens 3 is so designed as to form a plurality of concavo-convexzones, A, B and C, of different spherical diameters and having-radii 7,8, and 9, that portion of zone B enclosed within the heavy line 8w shownin Fig. 3, having a radius corresponding to line 8?), Fig. 1. The radiusof the outer convex surface is shown by the line 10.

It will be noted that these radii are of different lengths but thecenters are located in a central vertical plane.

A tubular reflecting shield 11 is mounted on a collar 12 formed integralwith the lens, and that portion of the lens within the collar having aformation to assist in the proper distribution of light. This centralportion 13 is convex on its inner face and is provided with a series ofparallel vertical grooves 14, the cross-sectional radius of thesegrooves being relatively small to cause a Wide divergence of the lightbeam, a radius of approximately and a width of groove of beingsatisfactory. The collar and enclosed lens are of greater lengthhorizontally than vertically which tends to give a lateral spread to thelight rays. The

, inner surface of the tube causes the rays from the filament to bedirected forwardly to the central lens which tends to bring them into ahorizontal plane and to give them a lateral spread. The rear edge ofthis shield 11 is substantially circular and so positioned as tointercept practically all of the direct rays from the light source whichwould otherwise escape as a widely divergent beam through the lens 3.The shield 11 may be cut away if desired, as shown at 15, to permit acertain amount of light to escape through the lens 3 to illuminate theside of the roadway.

In order to provide the desired light distribution, the lines dividingthe zones A, B, andC, are curved instead of being horizontal. The line16 between the intermediate and upper zones is concave upwardly from themiddle portion of the zones to the edge of the lens. The line 17 isconcave downwardly from the middle of the zones totheedge.

The moderately wide divergence of the beam through the upper zone A andthe lower zone C is accomplished by providing the inner face of thesezones with a series of parallel vertically extending concave grooves 18having a cross-sectional radius relatively small. It has been foundsatisfactory to make these grooves in width and with radius.

The slight divergence of the powerful beam through the intermediatezone, B is accomplished by providing this zone with a series of parallelvertically extending grooves 19, 20, 21, 22, and 23, havingcomparatively large cross-sectional radii.

In practice I have found a desirable light pattern to be obtained byhaving the central grooves 19 approximately radius and in width, thegrooves 20 approximately radius and in width, grooves 21 approximately 2radius and 7 in width, grooves 22 approximately 1% radius and wide, andthe grooves 23 relatively small in width and radius.

It will be noted that, due to the length and position of centers of theradii 7, 8, 8b and 9 of the three zones, and the convex curvature of theoutside surface of the lens, the lens is of constantly increasingthickness from the top to the bottom of each zone on any verticalsection, and that the thickness at the top of each zone is less than atthe bottom of the adjacent zone.

This is for the purpose of producing the desired vertical arrangement ofthe light pattern as illustrated in Fig. 2 in which the area 24indicates the area of highest light intensity, 25 an area of intensityapproximately one-third of that at 24, area 26 an intensity aboutone-sixth of 24, and 27 about one-tenth the intensity of 24. The area 28is caused by stray rays of very low intensity.

It will be noted from this diagram that it is desirable to maintain thearea of highest intensity near the top, and the areas 24, 25, and 26 aresuperimposed on the area 27. The area 24- having the highest intensityis produced from the beam through the grooves 21 and 22 of the middlezone B. Area 25 is produced through the grooves 19 and 20 of zone B.Area'26 is produced from the upper and lower zones A and C, and area 27is produced.- by stray rays in general from zones A and B. and throughthe tubular shield 11. The main rays passing through the shield and lensformation 13 fall on the area 25 and 26, the stray rays spreadingwidely, covering area 27 and fading out into pattern 28. i

It will be seen from studying the action of the rays projected from aparabolic reflector with various positions of the filament, that it isdesirable to tilt the rays coming from the upper portion of thereflector downward, and thatthose rays coming from the most remote upperportion should be tilted downwardly to a greater extent than thosecoming from thecenter, and furthermore, the degree of tilt shouldconstantly decrease from the top to the center.

It is also desirable to tilt the rays coming from the lower portion ofthe parabola downward, and those rays coming from the lowermost portionshould be tilted downwardlyito a greater extent than those coming fromthe center, the degree of tilt uniformly increasing from center tobottom.

In order that the beams from the zones should overlap each other andform the de-' sired light pattern, the beams are tilted as illustrateddiagrammatically in Fig. 7. The degree of tilt of zone A at the borderline between zones A and B as indicated by line 29 is greater than thetilt of zone B at that border line, as indicated by line 30, andfurther, the tilt of the beam from the border line of z ne B at 31 isgreater than the tilt :3); zone C at that line, as indicated by line Thedesired tilt of the rays is accomplished bya constantly varyingthickness of lens in each zone on any vertical section. This variationof thickness or tilt of lens in each zone is not in steps but in avarying sweep to match the action of rays caused by misplacement of thefilament, and successfully refocuses the ascending rays from the upperand lower portion of the parabolic reflector due to a back or frontposition of the filament with relation to the focal point, and causesthem to fall in correct relative position to the beams of highintensity. The angular rays from the upper part of the reflector willfall on the pattern of high intensity due to 'a front focus, and underthe pattern of high intensity due to a back focus.

The upper border of zone A will never ascend above the high intensitypattern of zone B and varying from this to barely overlapping the lowerborder pattern from zone The pattern from zone C varies according to theVarious positions of filament, so that its upper border falls under thepattern from zone B and coinciding therewith to the position under thepattern from zone A.

The angle of the ascending rays from the reflector caused by misplacedfilament varies with their location relatively to the vertical andhorizontal axes of the reflec tor; that is, rays on the transversehorizontal axial plane are substantially horizontal while those lying onthe vertical axial plane have the maximum amount of ascension ordescension. Therefore, in order to take care of these conditions, thedegree of downward tilt of the rays varies across the horizontalsections of the lens having the greatest degree of tilt at thecenter-most portion, this being true of any horizontal section, and theleast amount of tilt at the outermost portion, and this tilt should bein constantly increasing ratio toward the center.

This is illustrated by the lines 33, 34, and 35 representing the rays ona horizontal plane through the lens 3, the ray 33 being on the verticalcentral plane, the ray 35 from a remote point on a horizontal plane,

- and the ray 34 from a point intermediate 33 and 35. This is just theopposite condition to that in the vertical sections. The tilt ordownward angular PI'OjGOtlOIl, de-

creases in the vertical sections toward the center as shown by the'raysrepresented by the lines 33a, 3312, 330 and 3312. A

If the lens betheoretically divided int any number of vertical sections,the rays from the central vertical section has more tilt than the rayson a horizontal line at any other vertical section, and each subsequentVertical section more remote from the center has less tilt than thevertical section next adjacent and toward the center.

While I have shown only one embodiment of my invention it is obviousthat modifications may occur to those skilled in the art, and I desire,therefore, that my invention be limited only by the scope of theappended claims and by the prior art.

Having thus described my invention, what I claim and desire to secure byLetters Patent is:

1. An automobile headlamp construction comprising an electric lamp bulb,a concave reflector in which said bulb is mounted for directing the raysof light which fall thereon substantially parallel to the axis, meansfor intercepting and redirecting the cone of those light rays from saidbulb which do not fall on the concave reflector and which wouldotherwise pass directly out through the open front of the reflector,said. intercepting and redirecting means having provisions for effectinga materially greater spread of said light'cone laterally thanvertically, said intercepting and redirecting meansnot extendinglaterally or upwardly materially beyond the confines of a cylindricalsurface tangent to the light bulb and coaxial with the reflector wherebythe beam from the concave reflector is not materially interfered with,and said intercepting and redirecting means comprising a funnel havingits rear edge lying substantially in the surface of said cone'of raysand its front portion flat vertically and elongated laterally, and alens portion adjacent the front portion of said funnel having a greaterrefractive power laterally than vertically.

2. An automobile headlamp construction comprising an electric lamp bulb,a concave reflector in which said bulb is mounted for directing theraysof light which fall thereon substantially parallel to the axis, andmeans for intercepting and redirecting the cone of those light rays fromsaid bulb which do not fall on the concave reflector and which wouldotherwise pass directly out through the open front of the reflector,said intercepting and redirecting means having provisions for effectinga materially greater spread of said light cone laterally thanvertically, said intercepting and redirecting means not extendinglaterally or upwardly coaxial with the reflector whereby the beam fromthe concave reflector is not materially interfered with, saidintercepting and redirecting means comprising a funnel having its rearedge lying substantially in the surface of said cone of rays and itsfront portion flat vertically and elongated laterally, said reflectorbeing provided with an inwardly concave outwardly convex glass coverextending across the front thereof, a substantial portion of said funnelbeing within said concavity, whereby a long funnel is provided.

3. In an automobile headlight construction, the combination with aconcave open front reflector and redirecting means for redirectingforwardly and toward the axis of the reflector a substantial portion ofthe rays from the lamp which do not fall on the reflector and whichwould otherwise pass directly through said open front, of a lens infront of said redirecting means for receiving and again redirecting saidredirected rays whereby the rays which do not fall on the reflector maybe utilized and given the desired direction without materiallyinterfering with the rays reflected from said reflector, said firstredirecting means having provisions for effecting more concentrationvertically than laterally, and said lens having provisions for causinglateral divergence of the rays passingltherethrough.

4. In an automobile eadlight construction, the combination with aconcave open front reflector and means for concentrating the rays fromthe lamp which do not fall on the reflector and which would otherwisepass directly through said open front, of a lens in front of saidconcentrating means for receiving and redirecting said concentrated ra swhereby the rays which do not fall on t e reflector may be utilized andgiven the desired direction without materially interfering with the raysreflected from said reflector, said concentrating means havingprovisions for effecting more concentration vertically than laterally,and said lens being laterally elongated and having vertically extendinglens formations for causing lateral divergence of the rays passingtherethrough.

In witness whereof, I have hereunto subscribed my name.

ADIEL Y. DODGE.

